The present invention relates generally to rewinders for winding a web material from one or more parent rolls into smaller rolls or logs, and more particularly to an improved apparatus for severing or cutting the web once the desired length of web has been rewound.
High speed rewinder machines are used in the paper industry for producing consumer sized logs or rolls of bathroom tissue, paper towels, and the like, from large parent rolls of the material. The smaller logs are then cut transversely into individual consumer rolls of a desired length. The industry is continuously seeking ways and devices to improve the operating efficiency and reliability of the rewinders.
A critical operation in the timed operating sequence of the rewinders is web cut-off and subsequent transfer of the web leading edge. Once the appropriate measured length of web material has been wound from the parent roll(s) onto the log core, the web must be automatically severed and the leading edge of the web must be transferred to a new core to continue the rewinding process. It is critical that these steps are carried out with relatively great precision and reliability while the web is moving at high speeds.
Various types of cut-off systems have been developed in the art for performing the web cut-off operation. Reference is made to U.S. Pat. Nos. 5,285,977; 6,056,229; 4,919,351; and 4,487,377. One type of conventional rewinder utilizes a cutting blade design with a first retractable blade or blades configured on a main roller (“bedroll”) around which the web passes in its running path. A cutting roller (“chopper roll”) is disposed adjacent the bedroll and includes a cutting blade configured thereon. For web cut-off, the bedroll blades are driven from their retracted position to a radially extended position wherein they engage and move the web material away from the surface of the bedroll. Rotation of the chopper roll is synchronized with that of the bedroll so that a chopper roll blade intermeshes with the bedroll blades to sever the web. Examples of rewinders using this type of cut-off system include the “Centrum” and “250” rewinders from Paper Converting Machine Co. of Green Bay Wis.
To effectuate a clean cut of the web, it is important that the web is stretched across the bedroll blades and not allowed to slip relative to the bedroll. To aid in this regard, foam or resilient pads are typically mounted on the chopper roll adjacent to the chopper roll blade. These pads serve to press and stretch the web against the tips of the bedroll blades as the chopper roll blades enter between the bedroll blades. Unfortunately, this process subjects the pads to a great deal of stress and wear and the useful life of the pads is relatively short. In high speed operations, it is not uncommon to replace the pads at two hour intervals. Replacement of the pads requires the rewinder to be shut down and results in disruption of the winding operation and significant downtime.
The present invention relates to an improved web cut-off assembly that does not require resilient pads or foam material.